Why Some Chimps Are Smarter Than Others

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Chimpanzees don't just get their smarts by aping others — chimps,
like humans, inherit a significant amount of their intelligence
from their parents, new research reveals.

Researchers measured how well 99 captive
chimpanzees performed on a series of cognitive tests, finding
that genes determined as much as 50 percent of the animals'
performance.

"Genes matter," said William Hopkins, a neuroscientist at Georgia
State University in Atlanta and co-author of the study published
today (July 10) in the journal Current Biology. [ The
5 Smartest Non-Primates on the Planet ]

"We have what we would call a
smart chimp, and chimps we'd call not so smart," Hopkins told
Live Science, and "we were able to explain a lot of that
variability by who was related to each other."

Animal 'intelligence'

People don't usually talk about
animal intelligence, but rather animal learning or cognition.
American psychologists John Watson and B.F. Skinner developed the
notion of behaviorism in the early 20th century, which said that
scientists should study only the behavior of animals, not their
mental processes. This was the dominant approach until about
1985.

But in the last few decades, studies have shown convincingly that
animals are capable of cognition. What remained unknown was the
mechanism behind it, Hopkins said. Many studies of human twins
suggest that intelligence
is heritable, but few studies have looked at whether this is
true in other primates.

In the new study, Hopkins and his colleagues gave chimpanzees at
the Yerkes Primate Center, in Atlanta, a battery of cognitive
tests adapted from ones developed by German researchers for
comparing humans and great apes. The tests measured a range of
abilities in physical cognition, such as the ability to
discriminate quantity, spatial memory and tool use. The tests
also examined aspects of social cognition, such as communication
ability.

The researchers created a genetic pedigree of the chimps, showing
how they were related to each other. This would be like taking a
group of 300 random people, sticking them on another planet where
they could breed and have children, and testing their
intelligence 50 years later, Hopkins said.

About half of the variability in the chimps' performance on the
cognitive tests could be attributed to their relatedness, the
results showed. "I was a little surprised by that. It was higher
than I thought would be," Hopkins said.

In addition, neither the sex of the animals nor their rearing
history (whether they were raised by their mother or by humans)
seemed to affect cognitive performance, the researchers
found.

Nature vs. nurture

In humans, some people believe that intelligence is primarily a
result of schooling. But for chimps, this can't be a factor,
since they don't go to school, Hopkins said. "The fact that we
can establish this in an organism that has none of the baggage of
our social-cultural systems points strongly to the
role that genes play in their intelligence," he said.

Alex Weiss, a psychologist who studies nonhuman primates at the
University of Edinburgh in Scotland, who was not involved in the
study, said the findings were "really interesting, particularly
as these findings mirror what has been found for decades in
studies of human twins and human families." It provides just one
more example of the similarities
between chimpanzees and humans, Weiss told Live Science.

But while the results suggest that "nature" matters a bit more
than "nurture" for intelligence, Hopkins said other findings
don't support that interpretation. Environment and experience
still have an influence on cognitive performance. For example, if
you compare chimps that have been trained to use sign language to
ones that haven't, the trained animals do much better on
cognitive tests, he said. "So there's a case where nurture really
matters."

Curiously, the results of the study support the idea of general
intelligence, rather than the theory of multiple intelligences —
such as mathematical, verbal or musical ability — that American
psychologist Howard Gardner developed. General intelligence
suggests that individuals posses a general learning ability that
makes it likely that a person who possesses one form of
intelligence will posses others.

Next, the researchers will attempt to replicate their findings in
another colony of chimpanzees. They also hope to incorporate
brain scans of the chimps, to establish if heritable features of
intelligence correlate with specific structures in the brain's
cortex. Finally, they aim to look for specific genes correlated
with intelligence, to see how those might be passed down in the
chimpanzees.